Inhibitor Of Mitotic Kinesin Eg5 Research Articles

Synthesis of novel fatty acid 3,4-dihydropyrimidin-2-(1H)-one and antitumoral activity against breast and gastric cancer cells.

Monastrol is the best-known small compound from the dihydropyrimidinones/thiones (DHPMs) heterocycle family, a cell-permeable molecule recognized as an inhibitor of mitotic kinesin Eg5, that is over-expressed in tumor cells and is a very promising target for the development of new drugs for cancer. The lipophilic properties of the DHPMs have been demonstrated to be of pivotal importance in the design of new molecules. This work describes the synthesis and antitumoral activity of novel C5-substituted fatty-DHPMs against breast and gastric cancer cell lines. The compounds were synthesized via Biginelli multicomponent reaction from oleyl β-ketoester in good yields (40-72%) using a simple approach catalyzed by nontoxic and free-metal sulfamic acid. Among the compounds tested, the compound 10c, derived from 3-hydroxybenzaldehyde and urea, exhibited 77% cellular viability to normal cells (C2C12) and was selected to be evaluated against tumoral breast (MCF-7) and gastric (AGS) cell lines. The results obtained afforded an IC50 of breast cancer cells of 2.3 μM, qualifying the molecule as the most potent, and making it a promising compound for future experiments in vivo.

Photocontrolled Eg5 inhibitor of mitotic kinesin Eg5 composed of azobenzne and spiropyran derivatives

Kinesin Eg5 is one of the kinesin super family and has physiologically important roles. During eukaryotic cell division, it aids in the development of a bipolar spindle. Eg5 has been found to be overexpressed in cancer cells to accelerate mitosis. Therefore, kinesin Eg5 is the target of cancer therapy. Small chemical compounds which inhibit Eg5 have been developed as an anti-cancer drug. Surprisingly, these inhibitors bind to the same pocket of Eg5 composed of α2, α3, and loop5. The structure of these inhibitors, however, is not conserved.

In silico analysis of 3D QSAR and Molecular Docking studies to discover new thiadiazole-thiazolone derivatives as mitotic kinesin Eg5 inhibition

A series of twenty one thiadiazole-thiazolone derivatives which is a class of highly potent human mitotic kinesin Eg5 inhibitor reported from published article were studied through a series of computer-aided drug design processes such as three-dimensional quantitative structure-activity relationship (3D-QSAR) modeling, including comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) and Surflex-docking method using 17 compounds as training set. Both models showed good statistical quality and satisfying predictive ability (Q 2 = 0.617 and R 2 =0.919 for CoMFA ) and (Q 2 = 0.638 and R 2 =0.919 for CoMSIA ). The aim of this study was to explore 3D-QSAR approaches to propose new thiadiazole-thiazolone derivatives as Eg5 inhibitors for human mitotic kinesin. The CoMFA/CoMSIA contour maps were generated to provide the information about regions where the activity might be increased or decreased. Moreover, Based on the X-ray crystallized complex (PDB ID: 2UYM) molecular docking was performed on the most potent proposed Eg5 inhibitors using Surflex-dock method as an approach to investigate the stability of docked conformation and study the binding interactions in detail.

Kolaflavanone, a biflavonoid derived from medicinal plant Garcinia, is an inhibitor of mitotic kinesin Eg5.

Mitotic kinesin Eg5 remains a validated target in antimitotic therapy because of its essential role in the formation and maintenance of bipolar mitotic spindles. Although numerous Eg5 inhibitors of synthetic origin are known, only a few inhibitors derived from natural products have been reported. In our study, we focused on identifying novel Eg5 inhibitors from medicinal plants, particularly Garcinia species. Herein, we report the inhibitory effect of kolaflavanone (KLF), a Garcinia biflavonoid, on the ATPase and microtubule-gliding activities of mitotic kinesin Eg5. Additionally, we showed the interaction mechanism between Eg5 and KLF via in vitro and in silico analyses. The results revealed that KLF inhibited both the basal and microtubule-activated ATPase activities of Eg5. The inhibitory mechanism is allosteric, without a direct competition with adenosine-5'-diphosphate for the nucleotide-binding site. KLF also suppressed the microtubule gliding of Eg5 in vitro. The Eg5-KLF model obtained from molecular docking showed that the biflavonoid exists within the α2/α3/L5 (α2: Lys111-Glu116 and Ile135-Asp149, α3: Asn206-Thr226; L5: Gly117-Gly134) pocket, with a binding pose comparable to known Eg5 inhibitors. Overall, our data suggest that KLF is a novel allosteric inhibitor of mitotic kinesin Eg5.

Microwave-accelerated multicomponent synthesis and X-ray characterization of novel benzothiadiazinone dioxide derivatives, analogues of Monastrol

We demonstrate here a rapid and comfortable synthetic sequence to benzothiadiazinone dioxide (six-membered cyclic sulfamide) derivatives, analogues of Monastrol, which is known to be a specific mitotic kinesin Eg5 inhibitor. Fourteen novel compounds (1d–14d) were synthesized through three component Biginelli reaction, by condensation of aromatic aldehyde, sulfamide, and cyclohexane-1,3-dione. A wide range of substrates is compatible in this reaction, producing excellent yields (82–92%) in short time (5–10 min). The reaction is performed under solvent-free, catalysed by H2SO4/CH3COOH (1/9) using microwave irradiation. The structure of the obtained substances was confirmed by 1H, 13C, HMBC, HSQC NMR spectroscopy, IR spectroscopy, and mass spectrometry, as well as elemental analysis. A single crystal of the (4-phenyl-4,6,7,8-tetrahydro-1H benzo[c][1,2,6]thiadiazin-5(3H)-one 2,2-dioxide has been obtained after recrystallization in ethanol/acetone (9/1) and selected for X-ray study.

Morelloflavone as a novel inhibitor of mitotic kinesin Eg5.

Among 40 plant-derived biflavonoids with inhibitory potential against Eg5, morelloflavone from Garcinia dulcis leaves was selected for further testing based on in silico analysis of binding modes, molecular interactions, binding energies and functional groups that interact with Eg5. Computational models predicted that morelloflavone binds the putative allosteric pocket of Eg5, within the cavity surrounded by amino acid residues of Ile-136, Glu-116, Glu-118, Trp-127, Gly-117, Ala-133, Glu-215, Leu-214 and Tyr-211. Binding energy was -8.4 kcal/mol, with a single hydrogen bond formed between morelloflavone and Tyr-211. The binding configuration was comparable to that of a reference inhibitor, S-trityl-L-cysteine. Subsequent biochemical analysis in vitro confirmed that morelloflavone inhibited both the basal and microtubule-activated ATPase activity of Eg5 in a manner that does not compete with ATP binding. Morelloflavone also suppressed Eg5 gliding along microtubules. These results suggest that morelloflavone binds the allosteric binding site in Eg5 and thereby inhibits ATPase activity and motor function of Eg5.

Photochromic Inhibitor of Mitotic Kinesin Eg5 Composed of Spiropyran and Azobenzene Derivatives which Exhibits Multiple Isomerization States

Photochromic Inhibitor of Mitotic Kinesin Eg5 Composed of Spiropyran and Azobenzene Derivatives which Exhibits Multiple Isomerization States

Structure-activity relationship of pyrazolo pyrimidine derivatives as inhibitors of mitotic kinesin Eg5 and anticancer agents

Human kinesin Eg5 is a potential inhibiting site for cancer chemotherapy. Blocking metaphase by binding foreign inhibitors with Eg5 eventually leads to apoptotic cell death. Here, we report the pyrazolopyrimidine derivates as potent inhibitors of Eg5 that prevents mitotic kinesin progression. IC50 values were evaluated against the motor domain of Eg5 using steady-state ATPase assay. To better understanding, we have performed molecular docking simulation. It reveals that the interactions of the proposed inhibitors with both the allosteric sites (helices α2, α3 and loopL5, and helices α4 & α6). Out of fifteen pyrazolopyrimidine derivates, three compounds (12, 25, and 27) have shown significant inhibition of Eg5. The synthesized compounds (12, 25, and 27) were tested for their in-vitro anticancer activity against cervical cancer cell line (HeLa).

3D-QSAR Modeling of Some S-trityl-L-Cysteine Analogues as Inhibitors of Mitotic Kinesin Eg5 by CoMFA, CoMSIA and H-QSAR Methodologies

Background: Mitotic kinesin Eg5, a member of the kinesin superfamily, plays an essential role in cell proliferation while the regulated cell proliferation is essential for survival, but uncontrolled cell proliferation increases the risk of cancer. Therefore development of new efficient Eg5 inhibitors is very important in cancer chemotherapy. S-trityl-L-cysteine (STLC) and their analogues are known as potent allosteric inhibitors for Eg5. In the present work, we try to develop some 3D-QSAR techniques including CoMFA and COMSIA methods to modeling and prediction of the Eg5 inhibitory activities for new STLC analogues. The result of this study not only can use to predict the Eg5 inhibitory activities of untested chemicals but also to design more active chemicals. Method: The 3D-QSAR methods including CoMFA, CoMSIA, and H-QSAR methods were performed to study the structure anti-cancer activity relationship of STLC analogues. The analysis of the contour maps from CoMFA was used for design more active Eg5 inhibitors. Results: The constructed CoMFA and CoMSIA models produced statistically significant results with the cross-validation correlation coefficients Q2 of 0.608 and 0.5, noncross-validation correlation coefficients R2 of 0.988 and 0.943, standard errors SE of 0.0937 and 0.2, and predicted correlation coefficients R2pred of 0.925 and 0.761, respectively. The analysis of the steric contour maps from CoMFA showed sterically bulky groups (R1) in para position have a favorable effect on inhibitory activity. Also, the electrostatic contour map of CoMFA model suggests that the presence electron negative substituent in the meta and para position can increase the inhibitory activity. Conclusion: Based on the result of COMFA model newly compounds with good predictive activity have been designed and predicted. Our finding in design represents both factors affinity to Eg5 and physicochemical properties of inhibitor should be considered in design and synthesis. Keywords: 3D-QSAR, kinesin Eg5, STLC derivatives, CoMFA, CoMSIA, H-QSAR.

Design and synthesis of novel thiadiazole-thiazolone hybrids as potential inhibitors of the human mitotic kinesin Eg5

A novel series of 1,3,4-thiadiazole-thiazolone hybrids 5a–v were designed, synthesized, characterized, and evaluated against the basal and the microtubule (MT)-stimulated ATPase activity of Eg5. From the evaluated derivatives, 5h displayed the highest inhibition with an IC50 value of 13.2 µM against the MT-stimulated Eg5 ATPase activity. Similarly, compounds 5f and 5i also presented encouraging inhibition with IC50 of 17.2 µM and 20.2 µM, respectively. A brief structure–activity relationship (SAR) analysis indicated that 2-chloro and 4-nitro substituents on the phenyl ring of the thiazolone motif contributed significantly to enzyme inhibition. An in silico molecular docking study using the crystal structure of Eg5 further supported the SAR and reasoned the importance of crucial molecular protein–ligand interactions in influencing the inhibition of the ATPase activity of Eg5. The magnitude of the electron-withdrawing functionalities over the hybrids and the critical molecular interactions contributed towards higher in vitro potency of the compounds. The drug-like properties of the synthesized compounds 5a–v were also calculated based on the Lipinski’s rule of five and in silico computation of key pharmacokinetic parameters (ADME). Thus, the present work unveils these hybrid molecules as novel Eg5 inhibitors with promising drug-like properties for future development.

Novel Photochromic Potent Inhibitor of Mitotic Kinesin Eg5 Composed of Spiropyran Derivatives

Novel Photochromic Potent Inhibitor of Mitotic Kinesin Eg5 Composed of Spiropyran Derivatives

Synthesis and antitumoral activity of novel analogues monastrol-fatty acids against glioma cells.

Monastrol is a small cell-permeable heterocyclic molecule that is recognized as an inhibitor of mitotic kinesin Eg5. Heterocyclic-fatty acid derivatives are a new class of compounds with a broad range of biological activities. This work describes a comparative study of the in vitro antitumoral activity of a series of new long-chain monastrol analogues against rat glioblastoma cells. The novel analogues C6-substituted monastrol and oxo-monastrol were synthesized via Biginelli multicomponent condensation of fatty β-ketoester in good yields using a simple approach catalyzed by nontoxic and free-metal sulfamic acid. Following synthesis, their in vitro antitumoral activities were investigated. Notably, all analogues tested were active against rat glioblastoma cells. Superior activity was observed by analogues derived from palmitic and stearic fatty acid chains; these compounds were the most potent molecules, showing 13-fold higher potency than monastrol with IC50 values of 5.11 and 6.85 μM, respectively. These compounds could provide promising new lead derivatives for more potent antitumor drugs.

Synthetic studies on mitotic kinesin Eg5 inhibitors: Synthesis and structure–activity relationships of novel 2,4,5-substituted-1,3,4-thiadiazoline derivatives

The 2,4,5-substituted-1,3,4-thiadiazoline derivative 1a has been identified as a new class of mitotic kinesin Eg5 inhibitor. With the aim of enhancement of the mitotic phase accumulation activity, structure optimization of side chains at the 2-, 4-, and 5-positions of the 1,3,4-thiadiazoline ring of 1a was performed. The introduction of sulfonylamino group at the side chain at the 5-position and bulky acyl group at the 2- and 4-position contributed to a significant increase in the mitotic phase accumulation activity and Eg5 inhibitory activity. As a result, a series of optically active compounds exhibited an increased antitumor activity in a human ovarian cancer xenograft mouse model that was induced by oral administration.

Bioisosteric approach in designing new monastrol derivatives: An investigation on their ADMET prediction using in silico derived parameters

Medicinal chemists are facing an increasing challenge to deliver safer and more effective medicines. An appropriate balance between drug-like properties such as solubility, permeability, metabolic stability, efficacy and toxicity is one of the most challenging problems during lead optimization of a potential drug candidate. Insoluble and impermeable compounds can result in erroneous biological data and unreliable SAR in enzyme and cell-based assays. The weak inhibitory activity and non-drug-like properties of monastrol, the first small mitotic kinesin Eg5 inhibitor, has hampered its further development. In this investigation, a bioisosteric approach was applied that resulted in the replacement of C-5 carbonyl of monastrol with thio-carbonyl. Further lead optimization of drug-like properties was evaluated through in silico predictions by using ADMET predictor software. This minor structural modification resulted in upgraded human effective jejunal permeability (Peff) and improved permeability in Madin–Darby canine kidney (MDCK) cells. Furthermore, C-5 thiocarbonyl analogue of monastrol (named as Special-2) was found safe to administer orally with no phospholipidosis toxicity, no raised levels of serum glutamate oxaloacetate transaminase (SGOT) and no potential towards cardiotoxicity. Molecular docking study was also carried out to understand the binding modes of these compounds. The docking study showed high binding affinity of the designed compounds against KSP. Hence a combination of in silico ADMET studies and molecular docking can help to improve prediction success and these compounds might be act as potential candidate for KSP inhibition.

Biocatalysts for multicomponent Biginelli reaction: bovine serum albumin triggered waste-free synthesis of 3,4-dihydropyrimidin-2-(1H)-ones

Bovine serum albumin (BSA) promoted simple and efficient one-pot procedure was developed for the direct synthesis of 3,4-dihydropyrimidin-2(1H)-ones including potent mitotic kinesin Eg5 inhibitor monastrol under mild reaction conditions. The catalyst recyclability and gram scale synthesis have also been demonstrated to enhance the practical utility of process.

Abstract 1781: LGI147, a novel small-molecule inhibitor of the mitotic kinesin Eg5, shows anticancer effects in human hepatocellular carcinoma

Abstract Background: Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide, for which novel therapies are urgently needed. Recently, the inhibitors of mitotic kinesin Eg5 emerge as potential anticancer therapeutics. The aim of this study was to investigate the anticancer activity of a potent Eg5 inhibitor, LGI147, as targeted therapy of HCC. Method: Antiproliferative effect of LGI147 (kindly provided by Novartis), a highly selective inhibitor of mitotic kinesin Eg5, was tested in three liver cancer cell lines (Hep3B, HepG2, PLC/PRF/5). Cell viability was measured by trypan blue exclusion assay. Mitotic perturbation was visualized by immunofluorescence staining and confocal microscopy. Cell cycle profiles were assessed by flow cytometry. Apoptosis was estimated by analysis of sub-G1 fraction, Annexin V expression and immunoblotting of apoptotic proteins. Results: LGI147 induced a dose-dependent growth inhibition with IC50s ranging from 43.47 pM to 53.59 pM in the tested HCC cell lines. LGI147 treatment for 24 hours led to inhibition of Eg5 activity and induction of abnormal mitosis in a dose-dependent manner. Polypolar spindle defects in mitosis, disturbed cell cycle progression, and induction of apoptosis were observed in the HCC cells treated with LGI147. Conclusions: These findings show that LGI147 has potent anticancer effects in human HCC. Inhibitors of mitotic kinesin Eg5 may deserve further exploration as molecular targeted agents against HCC. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1781. doi:1538-7445.AM2012-1781

3D-QSAR Studies of Dihydropyrazole and Dihydropyrrole Derivatives as Inhibitors of Human Mitotic Kinesin Eg5 Based on Molecular Docking

Human mitotic kinesin Eg5 plays an essential role in mitoses and is an interesting drug target against cancer. To find the correlation between Eg5 and its inhibitors, structure-based 3D-quantitative structure–activity relationship (QSAR) studies were performed on a series of dihydropyrazole and dihydropyrrole derivatives using comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) methods. Based on the LigandFit docking results, predictive 3D-QSAR models were established, with cross-validated coefficient values (q2) up to 0.798 for CoMFA and 0.848 for CoMSIA, respectively. Furthermore, the CoMFA and CoMSIA models were mapped back to the binding sites of Eg5, which could provide a better understanding of vital interactions between the inhibitors and the kinase. Ligands binding in hydrophobic part of the inhibitor-binding pocket were found to be crucial for potent ligand binding and kinases selectivity. The analyses may be used to design more potent EG5 inhibitors and predict their activities prior to synthesis.

Structure–Activity Relationships and Molecular Docking of Novel Dihydropyrimidine‐Based Mitotic Eg5 Inhibitors

Dihydropyrimidine-based compounds belong to the first discovered inhibitors of the human mitotic kinesin Eg5. Although they are used by many research groups as model compounds for chemical genetics, considerably less emphasis has been placed on the improvement of this type of inhibitor, with the exception of two recent studies. Dihydropyrimidines can be divided into class I (analogues that bind in the S configuration) and class II type inhibitors, which bind in the R configuration. Herein we report the synthesis and optimization of novel class II type dihydropyrimidines using a combination of in vitro and docking techniques.

Abstract 4427: Efficacy of a novel mitotic kinesin Eg5 inhibitor in docetaxel-resistant non-small cell lung cancer cells

Abstract Lung cancer is the leading cause of cancer-related deaths in Japan and worldwide. Non-small cell lung cancer (NSCLC) accounts for a majority of lung cancer and docetaxel is one of the key drugs in the treatment of metastatic NSCLC in combination with platinum agents as first-line therapy and is also given as second-line monotherapy. However, most of the patients acquire resistance and fail to respond not long after the initial treatment. Development of novel therapeutics which is active in docetaxel-resistant NSCLC is necessary. Mitotic kinesin Eg5 is critical for proper bipolar spindle assembly during mitosis. It also plays an important role in cancer cell proliferation and has been thought to be a good target for cancer therapeutics. We have synthesized an S-trityl-L-cysteine (STLC) derivative Compound3 as a novel Eg5 inhibitor and previously demonstrated potent growth-inhibitory effect in a wide variety of cancer cell lines. In this study, we evaluated the efficacy of Compound3 in docetaxel-resistant NSCLC cell line PC-14/TXT. Compound3 showed potent growth-inhibitory effect in PC-14/TXT cells by MTT assay without cross-resistance to docetaxel. In order to study the mechanism of growth inhibition by Compound3, we performed flow cytometry analysis and evaluated the effects of docetaxel and Compound3 on cell cycle progression in PC-14 and PC-14/TXT cells. Docetaxel induced G2/M cell cycle arrest only in PC-14 cells but it did not in PC-14/TXT cells. Compound3 induced G2/M cell cycle arrest not only in PC-14 cells but also in PC-14/TXT cells. Compound3 induced increase of sub-G1 fraction in PC-14 cells, suggesting Compound3 induced apoptosis in PC-14 cells. On the other hand, we did not observe increase of sub-G1 fraction by Compouond3 treatment in PC-14/TXT cells. These results suggest Compound3 exerts growth-inhibitory effect in PC-14/TXT cells by cell cycle arrest and it has a differential growth-inhibitory property between PC-14 and PC-14/TXT cells. Effect of docetaxel and Compound3 on spindles formation was evaluated by immunocytochemistry. Docetaxel induced multipolar spindles formation in PC-14 cells but did not show any effect in PC-14/TXT cells. On the other hand, Compound3 induced distinctive monoastral spindles formation in both PC-14 and PC-14/TXT cells as early as 8 hours after the treatment. We performed immunoblot analyses to further investigate the effect of Compound3 on molecules relevant to Eg5. There was no correlation observed between the growth-inhibitory effect and the basal Eg5 expression level between two cell lines. No significant difference was observed between the cells in the status of spindle checkpoint kinases such as MAD2 and BubR1. Taken together, a novel mitotic kinesin Eg5 inhibitor Compound3 should be considered for further exploration and development as a novel therapeutic option for the patients with non-small cell lung cancer who failed docetaxel treatment. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4427.

Abstract 4430: A novel mitotic kinesin Eg5 inhibitor exerts the growth-inhibitory effect in cancer cells in a manner independent of induction of monoastral formation but dependent on KRAS mutation status

Abstract Mitotic kinesin Eg5 plays an important role in mitosis, as it is critical for proper bipolar spindle assembly. After the discovery of the first Eg5 inhibitor monastrol, a number of Eg5 inhibitors have been developed as anticancer drugs. We have previously synthesized a series of S-trityl-L-cysteine (STLC) derivatives as Eg5 inhibitors and demonstrated potent inhibitory effect on Eg5 ATPase activity and induction of mitotic arrest with characteristic monoastral spindles in HeLa cells. In this study, we evaluated the growth-inhibitory acitivities of novel STLC derivatives, Compound1, Compound2, and Compound3 by MTT assay in a wide range of human cancer cell lines derived from gastric (MKN1, MKN45, MKN74, NUGC3, NUGC4, NCI-N87), colon (C170, DLD1, HCT15, COLO205), pancreatic (AsPC1, BxPC3, SUIT2) and lung (PC-9, PC-14, H1975, H441, A549) cancers and investigated potential predictive biomarkers. Among the derivatives, Compound3 showed the most potent growth-inhibitory effect and sensitivity between cell lines showed marked differences, with IC50 values ranging from 0.134 to 7.14 μM. Pancreatic cancer cell line AsPC1 and non-small cell lung cancer (NSCLC) cell lines H441 and A549 which harbor KRAS mutation showed relatively high IC50 values compared to other cell lines without KRAS mutation. Compound3 induced G2/M arrest in all cell lines as early as 8 hours after the treatment by flowcytometry, while the increase of the apoptotic sub-G1 fraction was not observed in these AsPC1, H441 and A549 cells harboring KRAS mutation. These results suggested that differential sensitivity to Compound3 and attenuated induction of apoptosis by Compound3 were attributed to KRAS mutation. Induction of monoastral spindles formation by Compound3 was observed as early as 8 hours after the treatment not only in sensitive cell lines but in refractory cell lines such as AsPC1 and H441 cells by immunocytochemistry, suggesting the induction of monoastral spindles formation does not work as a predictive biomarker for clinical development. There was no correlation observed between the growth-inhibitory effect and the basal Eg5 expression level of each cell line by western blot analysis. No significant difference was observed in the induction of a spindle checkpoint kinase BubR1 phosphorylation among the cells, a potential predictive biomarker in response to the Eg5 inhibitor treatment by western blot analysis. Taken together, a novel mitotic kinesin Eg5 inhibitor Compound3 should be considered for further exploration and development and KRAS mutation status was suggested to be a candidate for a predictive biomarker of poor response to Eg5 inhibitors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4430.